Experimental analysis of wind farms connected to the high voltage grid: the viewpoint of power quality

The wind farm design is aimed at obtaining efficient and economic energy production, complying with regulatory requirements and grid operator specifications. In particular, a set of power quality requirements concerns limits in frequency and voltage variations, harmonics, flicker severity, unbalance, etc. in Medium Voltage (MV) networks. The paper deals with an experimental analysis of two Italian wind farms that was performed in order to check both performance and compliance to regulations. These farms are connected to the High Voltage network, by means of a MV-HV transformer, and are made up with variable-speed wind turbines, based on doubly fed induction generator (DFIG). The results obtained confirm that the HV connection reduces the voltage variations, so that they lie within the acceptable limits, and that the DFIG exhibits good performance concerning power factor, harmonics and flicker. Moreover, measurements show that the shape of the terrain plays a very important part on the power produced by the wind generators distributed over the farm.